Steady State and Pulsed Thermal Simulation of Gateless AlGaN/GaN Heterostructures

Due to the complex nature of the failure in reliability of GaN electronics, a multiphysics model was developed to describe the evolution of electrical, thermal, and mechanical stress fields in devices under operational conditions. Electrical, thermal and mechanical characteristics of an AlGaN/GaN transmission line measurement (TLM) structure were modeled under steady state and pulse operational conditions for varying input powers. The electric field and power dissipation in the device was determined by solving Maxwell’s equations while the peak temperature was obtained by solving the thermal energy equation. By coupling the solutions, the impact on device current-voltage characteristics was obtained. Under pulse conditions, devices showed higher currents and lower temperature rises owing to reduced Joule heating compared to steady state. Finally, a one way coupling to a thermo-mechanical model of the device allowed for the analysis of the thermal-induced stress fields which have an impact on the overall device reliability. It was found that the peak temperature and stress in the simulated device at 40 V in steady state was 765 K and −0.60 GPa, while in pulsed mode the peak temperatures and stress were significantly lower at 562 K and −0.38 GPa for a 5 μs pulse and 652 K and −0.48 GPa for a 25 μs pulse.